The blending of two of more polymers has attracted wide interest for a variety of reasons including the development of new "polymer alloys", new products, as well as the desire to recycle post-consumer plastic waste materials.
One of the technical difficulties with recycling of post-consumer plastic waste materials is the incompatibility of the different polymer materials found in plastic waste streams such as polypropylene, polyethylene, polystyrene, polyvinylchloride (PVC), polyesters, polyamides and others. Generally speaking blends of incompatible or thermodynamically immiscible polymers produce blends which exhibit poor mechanical properties and processing difficulties.
Moreover, post-consumer waste material is often collected as a mixture of incompatible polymer materials. One such system is polyethylene (PE) and polyethylene terephthalate (PET) which constitute a large portion of both rigid and flexible post-consumer plastic waste. These two polymers are immiscible and incompatible and therefore their blends exhibit poor mechanical properties and processing difficulties.
Although PET and PE can be physically separated due to differences in densities, the operation is capital intensive. An alternative has been the use of compatibilizing agents to lower the interfacial tension between the two phases. There have been a number of efforts in the past with different degrees of success to find such suitable compatibilizers.
For example, Traugott et al. utilized Styrene-Butadiene-Styrene (SBS) the block copolymer (sold under the trademark "Kraton") as a compatibilizing agent in blends of PET and high density polyethylene HDPE as disclosed in the Journal of Applied Polymer Science, Volume 28, p. 2947-59. A significant increase of Izod impact was reported by Traugott with the inclusion of 10% SBS's, but at the expense of tensile strength and modulus.
Japanese IP 91-228316 910813 relates to thermoplastic polyester-polyolefin molding compositions where the polyolefins are modified with unsaturated carboxylic acids or their derivatives, typically maleic anhydride and blended with copolymers of unsaturated carboxylic acid, glycidyl esters, typically glycidyl (meth) acrylate and other monomers.
Furthermore, Japanese J02276841, JP 02-276841 relates to an orientated film suitable as synthetic paper for blending a polyolefin resin with thermoplastic polyester and maleic anhydride modified or glycidyl methacrylate modified polyolefin resin.
Moreover U.S. Pat. No. 4,753,980 relates to toughened thermoplastic polyester compositions comprising polyester matrixing resin and ethylene copolymer such as ethylene/methylacrylate/glycidyl methacrylate.
It is an object of this invention to provide an improved composition for blending polyolefins and polyesters having improved mechanical properties.
The broadest aspect of this invention relates to the provision of a compatibilizer composition comprising a grafted polymer grafted with at least one monomer selected from ethylenically unsaturated dicarboxylic acids and anhydrides thereof, and derivatives thereof. One embodiment of the invention utilizes polyethylene grafted with maleic anhydride (PE-g-MAH) and ethylene, n-Butyl Acrylate glycidyl methacrylate (EnBAGMA).
Another aspect of this invention comprises blending polyolefins and polyesters with PE-g-MAH and EnBAGMA.